This invention relates to landscape architecture and to a structure and method for designing walkways and vehicle traffic areas that promote the growth of trees and other vegetation in close proximity thereto so as to enhance their overall utility and beauty.
Trees and adjacent hardscape surfaces are mutually incompatible. The hardscape surfaces, defined here as load-bearing, generally impervious, surfaces, such as concrete sidewalks, parking lots, and driveways that are necessary for the convenience of humans are usually supported on compacted soil or fill. Trees and similar vegetation, on the other hand, require nutrients and water, and send forth an extensive root structure in search of these elements that are essential to growth of the tree. The structural root system is destructive to the hardscape surface over time. The compacted soil beneath the hardscape stunts the growth of the root system and the growth of the tree.
There have been many proposals to solve the problem, which are unfriendly to tree root growth. These comprise “root barrier” systems that place an impenetrable, permanent shield between the tree roots and the subsurface beneath the hardscape. Exemplary of these “root barrier” systems are U.S. Pat. No. 4,019,279 issued Apr. 26, 1977 to Moorman and U.S. Pat. No. 5,070,642 issued Dec. 10, 1991 to Albrecht, which are cited to show well-known permanent root barrier or deflector systems protecting an adjacent, non-permeable hardscape.
A system that seeks to promote the growth of tree roots beneath an adjacent hardscape is seen in U.S. Pat. No. 7,080,480 issued Jul. 25, 2006 to Urban, et al. Urban discloses a structural cell system comprising a matrix of load-bearing cells of concrete composites or plastic stacked in horizontal layers with permeable barriers separating the layers into three groups. The cells are of an open design to allow water, soil and/or roots to penetrate. The center group has soil-filled cells while upper and lower groups are for short term and long-term water storage respectively. Tree root growth takes place in the center group filled with low compacted soil. The system is designed to capture storm water and pipe it to the upper and lower groups of stacked structural cells which serve to perform a load-bearing function to support the hardscape above. The system is designed to be installed under impervious hardscape such as sidewalk, parking or roadway pavement but may also be used under permeable hardscapes such as turf, planting beds or compacted soil. In either case, the hardscape is a permanent surface structure, requiring inspection ports, overflow pipes and soil injection pipes in order to reach the layers of structural cells below. Many layers of structural cells stacked on top of one another are required when using the aforementioned Urban system and there is no convenient way to augment the contents of the soil-filled root growing cells except through one or more soil injection ports.
A modified root barrier system is shown in U.S. Pat. No. 5,383,302 issued Jan. 24, 1995 to Hill, which describes a combination tree root disbursement system and tree root barrier system. An inner cylindrical structure with openings surrounds the root ball and an outer barrier structure is spaced from the inner structure to protect an adjacent concrete hardscape. The openings are designed to promote some horizontal growth through the openings. However, a permanent barrier prevents horizontal root growth beneath the adjacent non-permeable hardscape.
It would be desirable to have an inexpensive method and structure for controlling and enabling tree root growth adjacent a walkway or similar load-bearing surface. It would also be desirable to have a convenient way to periodically nourish the root growth zone with mulch, nutrients, loose loam, water and other elements necessary to healthy tree root growth. Furthermore, it would be desirable to plant trees adjacent a hardscape with an inexpensive root-friendly substructure beneath it that allows tree roots to gradually establish themselves over time, extending roots into the substructure.
Accordingly, one object of the present invention is to provide an improved method and structure for enabling tree root growth beneath adjacent load-bearing surfaces.
Another object of the invention is to provide a structure and method for periodically nourishing a tree root growth zone with elements necessary to healthy tree root growth.
Another object of the invention is provide a structure and method for laying out trees, walkways or parking areas with an inexpensive root-friendly substructure beneath the walkways or parking areas.
Another object of the invention is to provide a walkway with a root-friendly substructure to be located adjacent to trees that allows the tree roots to gradually establish themselves over time, extending roots into the root-friendly substructure.